Buggy code:
for ( Object o : ( ( Set < ? > ) ( obj ) ) ) { timestamps . add ( new DateUtils ( ) . formatIso8601Date ( ( ( Date ) ( o ) ) ) ) ; } return new AttributeValue ( ) . withSS ( timestamps ) ; } } ; } else if ( Calendar . class . isAssignableFrom ( returnType ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { List < String > timestamps = new LinkedList < String > ( ) ; for ( Object o : ( ( Set < ? > ) ( obj ) ) ) { timestamps . add ( new DateUtils ( ) . formatIso8601Date ( ( ( Calendar ) ( o ) ) . getTime ( ) ) ) ; } return new AttributeValue ( ) . withSS ( timestamps ) ; } } ; } else if ( ( boolean . class . isAssignableFrom ( returnType ) ) || ( Boolean . class . isAssignableFrom ( returnType ) ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { List < String > booleanAttributes = new ArrayList < String > ( ) ; for ( Object b : ( ( Set < ? > ) ( obj ) ) ) { if ( ( b == null ) || ( ! ( ( Boolean ) ( b ) ) ) ) { booleanAttributes . add ( "0" ) ; } else { booleanAttributes . add ( "1" ) ; } } return new AttributeValue ( ) . withNS ( booleanAttributes ) ; } } ; } else if ( ( returnType . isPrimitive ( ) ) || ( Number . class . isAssignableFrom ( returnType ) ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { List < String > attributes = new ArrayList < String > ( ) ; for ( Object o : ( ( Set < ? > ) ( obj ) ) ) { attributes . add ( String . valueOf ( o ) ) ; } return new AttributeValue ( ) . withNS ( attributes ) ; } } ; } else { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { List < String > attributes = new ArrayList < String > ( ) ; for ( Object o : ( ( Set < ? > ) ( obj ) ) ) { attributes . add ( String . valueOf ( o ) ) ; } return new AttributeValue ( ) . withSS ( attributes ) ; } } ; } } else if ( Collection . class . isAssignableFrom ( returnType ) ) { throw new DynamoDBMappingException ( ( "Non-set<seq2seq4repair_space>collections<seq2seq4repair_space>aren't<seq2seq4repair_space>supported:<seq2seq4repair_space>" + ( ( ( getter . getDeclaringClass ( ) ) + "." ) + ( getter . getName ( ) ) ) ) ) ; } else { if ( Date . class . isAssignableFrom ( returnType ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { return new AttributeValue ( ) . withS ( new DateUtils ( ) . formatIso8601Date ( ( ( Date ) ( obj ) ) ) ) ; } } ; } else if ( Calendar . class . isAssignableFrom ( returnType ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { return new AttributeValue ( ) . withS ( new DateUtils ( ) . formatIso8601Date ( ( ( Calendar ) ( obj ) ) . getTime ( ) ) ) ; } } ; } else if ( ( boolean . class . isAssignableFrom ( returnType ) ) || ( Boolean . class . isAssignableFrom ( returnType ) ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { if ( ( obj == null ) || ( ! ( ( Boolean ) ( obj ) ) ) ) { return new AttributeValue ( ) . withN ( "0" ) ; } else { return new AttributeValue ( ) . withN ( "1" ) ; } } } ; } else if ( ( returnType . isPrimitive ( ) ) || ( Number . class . isAssignableFrom ( returnType ) ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { return new AttributeValue ( ) . withN ( String . valueOf ( obj ) ) ; } } ; } else if ( returnType == ( String . class ) ) { marshaller = new ArgumentMarshaller ( ) { @ Override public AttributeValue marshall ( Object obj ) { <START_BUG> if ( ( ( ( String ) ( obj ) ) . length ( ) ) == 0 ) <END_BUG> return null ; return new AttributeValue ( ) . withS ( String . valueOf ( obj ) ) ; } } ; } else { throw new DynamoDBMappingException ( ( ( ( "Unsupported<seq2seq4repair_space>type:<seq2seq4repair_space>" + returnType ) + "<seq2seq4repair_space>for<seq2seq4repair_space>" ) + getter ) ) ; } } } argumentMarshallerCache . put ( getter , marshaller ) ; } } return argumentMarshallerCache . get ( getter ) ; } private boolean parseBoolean ( String s ) { } String getAttributeName ( Method getter ) { } Method getSetter ( Method getter ) { } ArgumentMarshaller getVersionedArgumentMarshaller ( final Method getter , Object getterReturnResult ) { } ArgumentMarshaller getAutoGeneratedKeyArgumentMarshaller ( final Method getter ) { } boolean isVersionAttributeGetter ( Method getter ) { } boolean isAssignableKey ( Method getter ) { } }

Fix:
if ( ( obj == null ) || ( ( ( ( String ) ( obj ) ) . length ( ) ) == 0 ) )